Communication system



April 19, 1949- J. A. KRuMHANsl. l-:TAL

coMMNIcATIoN SYSTEM 5 Sheets-Sheet l Filed Feb. 9, 1946 April 19 1949- J. A. KRUMHANsL ETAL COMMUNICATION SYSTEM 5 Sheets-Sheet 2 Filed Feb. 9,. i946 h W MN @E PMS. um r 11111 :@IW mw:

5ML W April 19, 1949.l J. A. KRUMHANSI. Erm.

COMMUNICATION SYS/TEM 3 Shee'tS-Sheet 3 Filed Feb. 9, 1946 IIL? H 7' TOR/VE Y Patented pr. '19, 1949 COMMUNICATION SYSTEM James A. Krumhansl, Rochester, N. Y., a'x'd Harold Goldberg, Baltimore, Md., assignorsfto Stromberg-Carlson Company, a corporationof New York i, Application February 9, 1946, serial No. 646.6156

13 Claims.

This invention relates to communication systems and more particularly to detecting means for such systems.

It has been proposed to transmit in-telligence in the form of a train of pulses spaced apart -or coded according to a function of time as well as a function of the amplitude of a modulating voltage representing the intelligence to be transmitted. `One 4object of this invention lis to Iprovide in suc-h la system an improved method of :and means for translating or recreating a close :facsimile of the original intelligence.

While our invention is particularly -useful in jpulse communication systems it is not limited thereto and the principles of the -detecting sys- '.'tem described hereinafter are also applicable to other forms of communication including amplitude modulation radio transmission systems. It is, therefore, another object of our invention to provide new `and improved detecting means for. communication systems generally.

The foregoing objects are achieved by providing a receiving system including an envelope detector. This detector may comprise two electron discharge devices, each including an anode, a cathode, Iand a control electrode or grid. The discharge devices are inversely connected, i. e., the anode of one is connected to the cath-ode of the other and the cathode of the yone is connected to the anode of the other. A capacitor is coninected between each of these anode-cathode con- :nections and ground. A voltage representing a .desired characteristic of the received signal is .applied across one of the capacitors. One or the other of the discharge devices is rendered conductive at predetermined times which causes the instantaneous charge on the capacitor receivingl the signal to be transferred to the other capacitor. The voltage appearing across the other capacitor is applied to a suitable audio system for reproduction.

Further objects and advantages will become apparent as the following description proceeds. For a better understanding of our invention, reference is made to the following description and to the accompanying drawings in which:

Fig. l is a schematic diagram illustrating the (cl. 25o-s) f? application of our invention to a 'pulse communil Apush-pull principles,

Figs. 4 and 5 are charts illustrating the operation of the circuit shown in Fig. 3,

Fig. 6 is a schematic diagram illustrating the application of your invention to an amplitudemodulated system, and

Figs. '7 and 8 are charts illustrating the operation of the circuit shown in Fig. 6.

Referring to Fig. 1, there is illustrated a receiving system adapted to receive space or positionmodulated pulses such as would be transmitted in the system shown, described and claimed in the co-pending applications of Harold Goldberg, Serial No. 646,614, filed February 9, 1946, and Serial No. 646,615, filed February 9, 1946, and assigned to the same assignee as the present invention. The receiving system of our invention includes a suitable antenna I, a combined local oscillator `and mixer unit represented by block 2, `and van I. F. amplier and second detector indicated by the block 3. If desired, the signals may then be limited or clipped so that `.all signals at this stage of reproduction are positive, pulses of constant amplitude. Means for accomplis-hing this purpose is not shown but is well known in the art.

There is provided means indicated by numeral. 4 for deriving a delayed pulse from each received pulse for causing operation of `a decoder 5 which in turn provides voltage for causing operation of the envelope detector 6 at predetermined times.

The delay circuit 4 utilizes ya blocking oscillator and makes use of the fact that the output of a blocking oscillator may not .be unidirectional, but may have considerable overshoot, i. e., during a part of a complete oscillation, the voltage reverses. The overshoot, of course, is delayed with respect to the main peak of the pulse by a definite time interval.

In order to amplify and sharpen the received pulses, there is -provided the blocking oscillator illustrated in Fig. 1 com-prising `an electron discharge device 1, transformer l il and R-C network 8 (of R-C product much greater than the time spacing between received pulses) including a resistance and a capacitance connected in shunt relationship between the cathode 9 of the discharge device 'l and ground. The upper end of the R-C network is connected to a suitable source of bias potential of such valu-e as normally to i prevent operation of the oscillator in the labsence of received pulses. Positive pulses from the second detector, or clipper stage, `if used, are sulpplied to the control electrode l2 of device 1 through winding I4 of the transformer l and 'trigger the oscillator or generator circuit to cause 3 a voltage to appear across the R-C network. Since the received pulses are differently spaced, a train of pulses will be produced having equal maximum amplitudes spaced similarly to the received pulses.

The transformer ID is provided with two additional windingstl aridel.Ev Theconnections gto these windings are made in such a manner rthat output voltages are reversed in sense, the sense of the voltage appearing across winding l being 4 tion of the cycle is halted earlier and vice versa. Obviously, the overshoot of the `pulses utilized to trigger the decoder takes Iplace at a definite time intenval preceding the next succeeding pulse. Therefore, lby operating the decoder by means of the delayed or overshoot pulse the envelope detector-is rendered-operativenpriorl-to the receipt l of the undelayed pulse by `a.time equalto the reversed or inverted with respect to that across the winding i3 and that appearing across winding I8.

The youtput from Windingl is applied to the decoder 5 which comprises a saw-toothi wave generator including an-electron disch-arge device I1 which may be a triode having an anode I8 connected to a sui-table sougcgof positive p o-gn.

ten'tial, a control electrode i9 connected to one terminal of winding I5 of transformer i0, -and a cathode 2D. An R-C network comprising resistorll and electric storagelmeans such as con- A denser 22 connected in parallel` -therewith is in,

serted between cathode@ andgrollnd.` The ft2-C constant; mustibe requalto the R-C constant of the coder in the transmittenas explained in the, abovefidentiedi. cio-pending@ i applications. The

other terminal of ,transformer winding2 `I5 is f grounded. Inasmuch as inverted pulses are ap-` pliedsto gridoiS, theovershoot portions of the pulsesdevelopeddn the delayafoircuit trigger the discharge devicewll to charge; condenser 22 to a maximum amplitude, Between; operations of devicell', the ,Voltagezacross condenser 22 decreases In order to Separafethe -envelopelfrom the sawtoothwaJVe-`i .1e. to detect theirninima of the pulses i in the decoder output, Athe demodulatoror enve.- lope detector B is provided. Theenvelope ide-f` tector. inthis formof our invention comprises two electrondischarge devcesv andf26 which may be of the'triode type finc luding11anodes i 2l .and .28

respectively,.gcontrol electrodesl and respectively; andbathodes4 3l andi-.32 :respectivelyii` Anode 2l is connected .to cathode 32, `cathode 3i is connected to anode,28,;and the control elec-l e trodes `are connectedftogether. ,The output fof the-'decoder is impressed ionthe connection loe-l` tween-anode28 andcathodeif,I Uninvertedor undelayed pulses substantially:corresponding in time to the;original..pulsesnareiiapplied .to the: control electrodes 29 and 30 by means. of a connection -betweenthe control electrodes and one terminaliof the winding 4Hi of. transformer I0, the:

other terminalof thewinding; i6 Ibeing grounded,

Electric storage means .such as acapacitor1 33 is connected between ground-and .the connection joining anode 21 to cathode 32.1V`

The recurring voltage -generatedziin the decoder andzappearing across the capacitor 22 is impressed on ,the anode 28 and cathode 3|#- As brieiiy ydescribed aboveithe voltage acrossl capacitori22 decays exponentially until the oscil-V lator or generatorisagain triggeredV andthe next charging voltage is generateds. The spacingbetween the charging periods is. dependent uponthel amplitudeof the original signal., :Thus, as the` amplitude of the signal voltage increases thegens i.

eratQrtriesers-fmore rapidlyfandfthadecay por-..

above-mentioned interval. The capacitor 33 is at that... time connected across the capacitor 22 throughwthe conducting path of one of the discharge devices so that capacitor 33 is charged to thesamefvoltage as that across capacitor 22 at thatinstant. v`The capacitance of capacitor 33 is made substantially less than that of capacitor 22 so that the voltage of capacitor 22 is substantially unalected'by the .transfer of charge from capacitor 22 to capacitor 23.

A doubleset of discharge devi-ces or tube elements is necessary, whether in a single envelope or .in theform of a pair. of tubes 25 and 26 as shown, y'because the voltage across capacitor 33 at any given time may be greater or lessthan that across capacitorJZ depending upon the direction of change `of the jvoltagelacross capacitor ,22. ;If 1

thef voltage across capacitor 33 is greater than,

that across1capacitori22., electron discharge `device 25 isrrendered conductiverwhereas, if the voltage,

acrosscapacitor 33 i=s less thanthat of capacitor 22electrondischarge device-26 is rendered conductive. 'Ihefdischarge devices areso biased that when the puise subsides conduction through discharge device525 or discharge: device 26 isrcutoff.

In the ,embodiment of our invention illustrated in l Figfxl theinecessary negative bias is supplied through aresistord connected between the con.

trol electrodes and a1 suitable` source `of negative potential.; .,;Howe.ver,.the potentialat the upper end'of resistonZl andcondenser` 22 is;never nega.-

Uiveso that in effectthe control electrodesz29 and f 30 derive a negative'ibias from the `R-C network In order: to prevent'. transients, `there may be provided. a'v-resistorf35 in theconnectionbetween -f l thetransfor'mer Windingil and the control electrodes 29 and 30. .i

In iorder :.to prevent,l substantial decrease in charge acrosscondenser 33 Aduring the intervals between `samplings of the voltage `across-'condenserlZZ or, `in other words, when neither of the discharge devicesl25 and 2li-is cnducting,theout puti fronrthe condenser-33 is connected to the.

4audio system (not shown). through a high impedance device whereby discharge between .pulses is prevented.r In Fig; Il, the Vhigh impedance device takesthefformof a'cathode. follower, including an electron discharge dewice 38 which may be a trij oda; The ynpper end of condenser 33 is connected to the control electrode 39 of the discharge device L 38.-, `yThe eathodelnu of; the discharge device iS conitor 33 between pulsea.

Referring to Eigz, the I"itillline represents i the voltage appearing across capacitor. and, of

course, is alsonrepresentative of thevoltage appearing acrossresistance 4|.,4 Thisuvoltage may be ltered and fedto suitable audio system `for reproduction into sound.

InfFigLrS there'is illustrated-a modification of our invention utilizing push-pull-detection forl use 'n with a push-pull pulse transmission system such as that disclosed in co-pending application Serial No. 646,615 referred to above. The transmitted signals are intercepted on a suitable antenna 4Z connected to asuitable local oscillator and mixer stage 43 provided to translate the signal into a suitable intermediate frequency. The intermediate frequency signals are amplied and detected in the intermediate frequency ampliiier and second detector represented by the block 44. The positive pulses derived from the second detector are supplied through the winding 45 of the transformer 46 to the envelope detector 41 which serves as a push-pull demodulator and functions to detect the envelopes of the alternate minima, and to combine the resulting push-pull output through the agency of a delay circuit 48 and decoder 40.

` Delay circuit 48 comprises a triggered blocking oscillator including an electron discharge device 50, illustrated as of the triode type having a cathode 5|, a control electrode 52 and an anode 53. The blocking oscillator not only serves as a source of pulses for a timing wave but also as a pulse amplifier, Sharpener, and clipper. The R-C network 54 connected in the cathode lead provides a bias voltage for the control electrode or grid 52 which normally keeps the oscillator -circuit from oscillating. A positive pulse from the second detector triggers the -oscillator circuit and causes it to generate a single blocking oscillator pulse. The oscillator pulses are of constant amplitude and because of their form it is possi-ble also to obtain a delayed pulse as described above by reversing the sense of the output pulse from the transformer and utilizing the overshoot as a trigger pulse, the delayed pulse or overshoot thus providing a means for obtaining a delayed pulse without the use of delay networks. The delayed pulse appearing on the anode 53 of the electron discharge device 50 is transferred to the decoder 49 by means of primary winding 55 and secondary winding 56 of transformer 51. The decoder 49 comprises a :saw tooth generator including an electron discharge device 58 having an anode 59 connected to a suitable source of positive potential, a control electrode 60 connected to the secondary winding 56 of transformer 51, and a cathode 6| connected to ground through an R-C 'network consisting of resistance 62 and capacitor 63 connected in shunt relationship. The delayed pulse is thus applied to control electrode 60 to cause the generation of a voltage each time a pulse is received. A positive pulse applied to the v'control electrode of the decoder causes the condenser 63 to charge to a xed value. The subcapacitively coupled Ito diodes 63 and 69 respectively. The diodes act as direct current restorers.

'The output of restorer 68 is added to the pulse in secondary winding 10 of transformer 51 and the 4output of diode 69 is added to the received pulse in secondary winding 1| of transformer 46.

The push-pull envelope detector 41 may corn- `prise four electron discharge devices 13, 14, 15, and 16. Cathode 11 and anode 18 of discharge devices 13 and 14, respectively, and anode 10 and cathode' of discharge devices 15 and 16, re-

spectively, are connected together and to the upper end of capacitor 63 of decoder 49. Anod-e 8| and cathode 82 of electron discharge devices 13 and 14, respectively, are connected to the upper side of capacitor 83 as Viewed in Fig. 3. Cathode 84 and anode 85 of discharge devices 15 and 16, respectively, are connected to the lower side of a capacitor 86. The lower side of capacitor 83 and the upper side of condenser 86 are connected together and to ground. The combined voltages appearing in transformer winding 10 are applied to the control electrodes 81 and 88 of electron discharge devices 13 and 14, respectively, and the combined voltage appearing acrosswinding 1| is applied to control electrodes 36 and 90 of discharge devices 15 and 16, respectively. In this manner the two envelope detectors will be activated alternately and each by itself determines the alternate minima of Athe decoder, and the outputs of the two detectors are, therefore, push-pull variations of the original modulation.

The two detectors are respectively coupled by the condensers 83 and 86 to cathode followers including the electron discharge devices 9| and 92. The transform-er winding 93 in the cathode circuits of the followers combine the push-pull outputs through a secondary winding 94 to a suitable output circuit for reproduction.

Fig. 4 depicts the action taking place in the circuit of Fig. 3. As stated above the voltage appearing across the condenser 63 is represented by the numeral 64 in Fig. 4. The dashed line 05 represents the charge on one of the condensers as, for example, condenser 83 and the dashed line 06 represents the voltage on the other condenser 06. The resultant or combined lvoltage is shown by the stepped line 91 of Fig. 5. In each of Fi-gs. 4 and 5 the envelope of the minima which is the signal to be reproduced is represented by the numeral 08.

Our invention is not limited to pulse systems. For example, it is also applicable to amplitude modulation, particularly in cases where the envelope frequency is not much lower than the The output of the second detector is fed to a cathode follower circuit including an electron discharge device |03 including an anode |04 connected to a suitable source of positive potential, a control electrode |05 connected to the output `of the second detector and a cathode |06 connected to ground through a resistor |01. A capacitor |08 is connected in shunt with the resistor |01. The time constant of capacitor |08 and resistor |01 should be short so that the condenser discharges before it is re-charged by operation of discharge device |03. The Voltage appearing across the capacitor |08 is applied to one of the inversely connected electron discharge devices |06 and H0 respectively in similar manner -to that illustrated in Fig. 1. C-ondenser lll is connected between ground and the other anodecathode connection as well as to a cathode follower output device I|2. It will be noted that thedelayed voltage is applied to the rst mentioned anode-.cathode connection. the. system shown in Fig. 6v` itisfnot desired to compare the voltage changes priorl .to the reenergization of the discharge device |03was was the casein the pulse receiving system, but itis. desired. to sample the voltage across capacitorl. at the peaks oi the `modulated carrier waves.V Inorder to render conductive one or the otherl of the discharge devices |09 and ||0 the output of the second detector is fed through .means H3` for clipping the signal, means l lllor squaring the clipped signals and differentiating means .|I5 comprisinga capacitor I I6 and a resistance l| 1 to provide, trigger pulsesior a delay multi-.vibrator IIB. The operation of the system shown inF-ig.. 6 is illustrated in Fig. 7 wherein at A thereare illustrated a` few cycles of the modulatedcarrier, at B. the squared waves appearing. in the output of means I4, and at C the peaked pulses derived from the diierentiating means which are applied 'as trigger pulses to the multifvibrator H8. The multi-vibrator comprises discharge devices |19 and |20, the circuit connections being such that device H9 is normally non-conductive and device |20 normally conductive. The trigger pulses applied to the control electrode |.2I of electron discharge device ||9 render that device conductive and discharge device |20 non-conductive to establish positive pulses at the anode of d-evice |20. These pulses are impressed on a blocking oscillator comprising an electron discharge device |3| which may be a triode havingan anode |32, control electrode |33 and cathtode |34. An RjC network of suitable R-C product is connected between the cathode and -ground and compris-es resistance |38 and capacitor |39. 'The pulses are impressed on anode |32 through a suitablecoupling capacitor |4| and also to one end of winding |35 of trans-.- former |36, the other end of winding .being connected to a suitable source oi positive pQtn tial. Winding |31 of transformer |36. is connected from ground to control electrode |33 through a suitable grid leak-gridcondenser com.- bination. The cathode |34 is also connected through resistance |40.to a. suitable source of positive potential, thereby establishing bias for discharge device |3|. Capacitor |4| and winding 35 serve to differentiate the pulses, .the negative going' pealr of the differentiated pulses appearing as positive voltage pulses in winding |431,

causing conduction in device 3|. The dip in anode voltage is transformed into a positive pulse in winding $42 of transformer |36.

These pulses are applied to the control electrodes i2! and |22 of the electron discharge devices |63 and H0 respectively of theenvelope.

detector. Whenever either of the Adischarge devices lg and H0 .becomes conductive, capacitor lll assumes the voltage appearing. across |08 capacitor at that instant. As. seen in Fig. 8, lif the envelope detector operates at kthe peaks of the carrier current wave, the voltage across capacitor l l is stepped as indicated bythe numeral |23 in Figi). In Fig. 8 the carrier voltage is represented by the numeral` |24 and the envelope by the numeral |25. 'v

To enable adjustment of the circuit to cause sampling and equalization of capacitor voltages at the carrier ,peaks there is provided, means for v adjusting the bias .on the control' electrode of particularly critical inasmuch as the relativelyl gradual change involtage over a relatively long period of. time at the peak of the carrier wave will. give substantially the same results as can be seen 'by reference to Fig; 7, D. While, conditions are, exaggerated for purposes of illustration, .it will. be seen that if the pulses derived from the multi-vibrator occur at any time. between the dotted positions indicated by the numeral |.30 thevoltage across capacitor Ill will be. .diierent onlyto a minor degree from that which would result if the envelope detector operated at exactly the maximum of the carrier wave.

The circuit of Fig. 6 may be simplified by omitting the last mentioned blocking oscillator I 3| and, transformer |36. Instead, the negative pulses appearingA at the anode of discharge device ||9 canl be diierentiated and the positive going part of the diierentiated pulse employed to trigger the envelope detector.

While we have shown and described particular embodiments of our invention it will be obvious to thoseskilled in the art that changes and modfiiications may be made without departing from our invention in its broader aspects and we, therefore, aim in the appended claims to cover all such changes and modificationsV as fall within the true spirit and scope of our invention.

What wey claim as new and desirey to ,secure by letters Patent of theUnited States, is:

1,.,.In a communication system having trans,- mitting means and receiving means, the receiving means including means for detecting intellif gence to be reproduced including a pair of elecf. trondischarge devices, each of said devices h aving an anode, a cathode, and a control electrode, means for inversely connecting,l said anodes and cathodes and means for connecting saidcontrol electrodes,.one of said anode-cathode connections constituting a rst input terminal and said .control electrode connection constituting a second input terminal to said detecting means. a first electric storage means connected between said first input terminal and ground,V a

.means for impressing a, voltage representing the .signal whereby the potential of said rst electric s torage means is transferred to said second electric storage means during such conductive periods.

` 2. In a communication system having trans,- mitting and receiving means, said. receiving means including means for detecting the intellihgence to. be reproduced including a pair of electron-discharge devices, each of which devices has an anode, a cathode, and a control electrode, said anodes and cathodes being inversely connected and said control electrodes being con.- nectedA together, one of said anodeecathode connections constituting a iirst input terminal of saiddetecting means and said control electrode connectionv constituting a second input terminal, a third electron discharge device having an anode, a cathode and a control electrode, a resistance connected between the cathode of said third .discharge device and ground, a irst capaci- ',tanceA connected in shunt with said resistance, a second capacitance connected between the other .anode-cathode connection and ground, means for `impressing a voltage representing the received signal on the control electrode of said third device whereby the charge on said first capacitance rcorresponds to a characteristic of the received signals, the ungrounded end of said rst capacitance being also connected to said rst input terminal whereby the potential of said first calpacitance is transferred to said second capacitance whenever either of said pair of electron discharge devices is rendered conductive, and means for rendering one or the other of said pair of electron discharge devices conductive at desired times.

3. In a communication system having transmitting and receiving means, said receiving means including means for detecting the intelli- 1 gence to be reproduced including a pair of electron-discharge devices, each of which devices y has an anode, a cathode, and a control electrode, .said anodes and cathodes being inversely con- 'nected and said control electrodes being connected together, one of said anode--cathode conl,nections constituting a first input terminal of 4said detecting means and said control electrode connection constituting a second input terminal, i a third electron discharge device having an anode, a cathode and a control electrode, a resistance connected between said cathode of said third discharge device and ground, a rst capacitance connected in shunt with said resistance, a second capacitance connected between the other anode-cathode connection and ground, 1 means for impressing a voltage representing the .received signal on the control electrode of said kthird device whereby the charge on said first capacitance corresponds to a characteristic of the received signals, the ungrounded end of said rst capacitance being also connected to said first input terminal whereby the potential of said rst capacitance is transferred to said second capacitance whenever either of said pair of electron discharge devices is rendered conductive, means for rendering one or the other of said pair of electrondischarge devices `conductive at desired times, and high impedance output means coupled to said second capacitance.

4. In a communication system having means for transmitting and receiving signals, said receiving means comprising means for detecting intelligence to'be reproduced including a pair of `,electron-discharge devices, each of which devices has an anode, a cathode,'and la control electrode, said anodes and cathodes being inversely connected and said control electrodes being connected together, one of said anode-cathode connections constituting a rst input terminal to said detecting means and said control electrode connection constituting a second input terminal, a rst capacitance connected between said first -input terminal and ground, a second capacitance connected between the other anode-cathode connection andground, meansl for impressing a voltage representing the received signal on said first input terminal, and means actuated by the received signal and coupled to said second input terminal to render conductive one or the other of said electron discharge devices depending, upon relative potentials at the anode-cathode connection at predetermined times with respect to the received signal, whereby the potential of said rst capacitance is transferred to said second capacitance during such conductive periods, the

'10 capacity of said second capacitance being substantially less than that of said first capacitance so that the potential on said first capacitance is not substantially aiected by the transfer of potential from said rst to said second capacitance.

5. In a communication system including means for transmitting and receiving pulses representing intelligence to be communicated, said receiving means including a pair of electron discharge devices, each discharge device having an anode, a cathode and a control electrode, said anodes and cathodes being inversely connected, means for impressing the received pulses on said control electrodes, electric storage means connected between each anode-cathode connection and ground, means for reproducing each received pulse after a predetermined time delay, means for charging one of said storage means in accordance with the voltage of said delayed pulse, and means for applying said voltage to said second storage means whenever either discharge device is rendered conductive.

6. In a communication system including means for transmitting and receiving pulses representing intelligence to be communicated, said receiving means including a pair of electron discharge devices each having an anode, a cathode and a control electrode, said anodes and cathodes being inversely connected, means for impressing the received pulses on said control electrodes, electric storage means connected between each anode-cathode connection and ground, means for reproducing each received pulse after a predetermined time delay, means for charging a first of said storage means in accordance with the voltage of said delayed pulse and means for applying said voltage to the second of said storage means whenever either discharge device is rendered conductive, said second storage means having a capacitance substantially less than the capacitance of said first storage means so that the voltage on said rst storage means is substantially unaffected by the transfer of voltage to said second storage means,

7. In a communication system including means for transmitting and receiving pulses representing intelligence to be communicated, said receiving means including a pair of electron discharge devices, each of said devices having an anode, a cathode, and a control electrode, said anodes and cathodes being inversely connected, means for impressing voltages representing the received pulses on said control electrodes. a capacitor connected between each anode-cathode connection and ground, a source of recurring voltage, means for controlling the time of recurrence of vsaid recurring voltage in accordance with a characteristic of the received pulses, and means for applying said recurring voltage to one capacitor whereby the potential of said capacitor is applied to the other capacitor whenever either disl charge device is conducting whereby the changes in voltage across said other capacitor follow the voltage representing the intelligence transmitted. 8. In a communication system including means l :for transmitting and receiving pulses representtion and ground, a source of recurring voltage,

tron discharge devices, each of said devices having an anode, a cathode, and a control electrode, said anodes and cathodes being inversely connected, means for impressing voltages representing the received intelligence on said control electrodes, a capacitor` connected between each anode-cathode connection and Y ground, a wave generator including an electron discharge device and a resistance-capacitance network, said generator being normally inoperative, means for impressing a delayed counterpart of said signal on the control electrode' of said electron discharge device for rendering operative said generator to produce a voltage across said network, and means 'for impressing said voltage on one of said anodecathode connections, a capacitor connected between the other anode-cathode 'connection and ground whereby the voltage generated by said generator i's applied to said capacitor whenever said generator is operative.

10. In a communication system including means for transmitting .and receiving pulses representing intelligence to be communicated, said receiving means 'including 'a pair of electron discharge devices, each of said devices having an anode, a cathode and Va vcontrol electrode, said anodes and cathodes being inversely connected, means for impressing said pulses 'on said control electrodes, means for obtaining a delayed counterpart of said ,pulsesjthe delay vinterval being less than the interval between successive pulses,

a rst capacitor connected to be charged by said counterpart, means permitting Vat least partial dissipation of 4said charge between charging intervals, means for impressing the potential of said rst capacitoro'nbne of said'anode-cathode connections, and a second capacitor connected to the other of saidanode-cathode connections whereby said second capacitor samples the charge on said iirst capacitor Vduring conduction of either of said discharge devices, the voltage across said second capacitor reproducing closevly the voltage corresponding to theintelligence transmitted.

11. In a modulated .wave "communication system having means for transmitting and receiving modulated signals, said receiving means 'including means for reproducingthe vintelligencereceived from said transmitting means, said means including a pair `of electron discharge Hdevices, each device having an anode, acathode and a control-electrode, said'anodes .and 'cathodes being inversely connected, a capacitor connected between each anode-cathode 'connection and ground, means for impressing a voltage 'corresponding to the modulated signals on'one oisaid anode-cathode connections, yand means --utilizing the received signal and said control electrodes for rendering conductive 4one or the other of said discharge devices atsubstantiallyfthe peaks of each cyclefof the received-'signal carrier whereby the voltage of -the capacitor connected tohsaid one anode-cathode connection is `applied 4*to the other capacitor each time either discharge-device 1is rendered conductive.

12. In a modulated wave communication sys- `tem including transmitting and `receiving means, said receiving means-'including means for detecting and `reproducing the 4received intelligence comprising a pair of electron discharge devices, each Aof said discharge devices having ananode, a cathode, and a control electrode, said anodes and cathodes being yinversely connected, a third electron discharge vdevice having an anode, `a cathode, and control electrode, resistance means connected `between the last mentioned cathode and ground, capacitance means connected in parallel with lsaid resistance means, means for impressing the received signal `onthe control electrode of said third'fdischarge device, means-for impressing the voltage appearingV across said capacitance `means von one of the anode-cathode v-connect-ions, capacitance means :connected-between the other vanode-cathode Lconnection and ground, and means for renderingone or the other of said discharge -devices operative at predetermined times-whereby Vthe potential of said iii-st capacitance'means is transferred `to said second capacitance means.

13. The method of reception off'pulse modullated signals which comprises` receiving ysaid pulses, developing :a voltage =of a given `value for 'each-pulse developinga second voltage corresponding to the 'rstmentioned voltage l"but delayed in time; =dissipating said second Avoltage in accordance-with-a `function of time ior'an interval terminated byfthe succeeding pulse in -the `Ytrain whereby the minima. ofthe said 4second `voltages at the termination of -the several intervals denean envelope-corresponding tothe origina'l signal, Autilizing said -flrst'yoltage to sample -said second voltage' at approximately the times 'of occurrence Aof said minima, and Ktranslating Athe sampled voltages yinto sound;

JAMES/A.' KRUMHANSL. HAROLD GOLDBERG.

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